1. Field of the Invention
The present invention relates to a telephone relay technique, and in particular, to a technique to relay a call between a telephone set capable of connecting to a plurality of telephone networks and a counterpart device.
2. Description of Related Art
A telephone device capable of connecting to a plurality of telephone networks has been in practical use. Japanese Patent Laid-Open Publication No. 2005-94646 describes a VoIP (Voice over Internet Protocol) compatible router capable of connecting to an IP (Internet Protocol) network and a PSTN (Public Switched Telephone Network). The VoIP compatible router includes a telephone number memory which stores IP telephone numbers and PSTN telephone numbers by associating them and a telephone number conversion processor which converts a PSTN telephone number inputted by a user to an IP telephone number, and a dial origination block of the VoIP compatible router performs call origination processing with an IP telephone number.
FIG. 30 shows a communication network for a telephone device capable of connecting to a plurality of telephone networks. In FIG. 30, a telephone device 101 is capable of connecting to a third generation mobile telephone network (3GCS) 102 and a wireless LAN (WLAN) 106. To the telephone device 101, a telephone number C of the 3GCS is allocated for line connection over the mobile telephone network 102 and a telephone number W of WLAN is allocated for line connection over the wireless LAN 106.
The mobile telephone network 102 is connected to a SIP (Session Initiation Protocol) server 108 and to the Internet 109 respectively via a media gateway (MGW) 104. The wireless LAN 106 is connected to the SIP server 108 and to the Internet 109 respectively via a router 107.
When the telephone device 101 makes a call using the mobile telephone network 102, the telephone number C for 3GCS is used, and a call is made via the mobile telephone network 102, the media gateway 104 and the Internet 109. When the telephone device 101 makes a call using the wireless LAN 106, the telephone number W for the wireless LAN is used, and a call is made via the wireless LAN 106, the router 107 and the Internet 109. Connections between the telephone device 101 and the mobile telephone network 102 and the wireless LAN 106 are made by wireless communications of different types, respectively. Call connection control is performed by the SIP server 108.
However, the conventional art involves such a problem that a plurality of telephone numbers associated with the terminal (i.e., one for the mobile telephone network 102 and one for the LAN 106) cannot be associated on the communication network side, so the terminal cannot originate and receive calls with one telephone number.